Square has just made a key hire, poaching Facebook’s director of ad products Gokul Rajaram to be its product engineering lead.

Mr. Rajaram, who had been at Facebook since September 2010 and played a critical role in spearheading the development of new ad products, will lead development for Square Register, a point-of-sale system for businesses, and other products. He was also instrumental in Facebook’s acquisition of Microsoft’s ad server Atlas.

“I’ve been fortunate to work for two mission-driven, world-changing companies, and Square’s vision and passion for helping businesses grow is inspiring,” he said, in a statement. “I’m thrilled to join the team and help build amazing products that drive economic growth and empower local businesses around the world.”